Apparatus for controlling a machine tool during the machining of a first workpiece to be matched with a second workpiece already machined

Abstract

The invention relates to an apparatus for controlling a machine tool during the machining of a first workpiece to be matched with a second workpiece already machined. The purpose of the invention is that of solving the problem to obtain the desired play along the entire matching section. For grinding a shaft to be matched with a bore, the apparatus comprises two pairs of measuring heads which check corresponding diameters of the shaft and of the bore, near their ends, a control unit for correcting the shape error of the shaft, preferably after a spark-out phase and before finish-grinding, and a control unit which controls the finish phase for obtaining the desired play.

What is claimed is: 
     
       1. Apparatus for controlling a machine tool during the machining of a part of a first workpiece to be matched with a part already machined of a second workpiece, comprising: first measuring means adapted to cooperate with said part of the first workpiece for providing a first signal and a second signal for checking respectively two dimensions on two distinct sections of said part of the first workpiece;   second measuring means adapted to cooperate with said part already machined for providing a third signal for checking a dimension of the part already machined; and   processing and control means coupled to the first and second measuring means to receive said first, second and third signal, the processing and control means being adapted to process the first and second signal for controlling and regulating the machine tool for correcting the deviations of the part of the first workpiece from a determined shape and to process the first and the third signal for controlling the machine tool for obtaining a pre-set matching between said parts.   
     
     
       2. The apparatus according to claim 1, wherein said parts have circular cross-sections, said first and second measuring means are adapted to check diameters of cross-sections of the parts and said processing and control means are adapted to correct the deviations from cylindricity or taper of the part of the first workpiece. 
     
     
       3. The apparatus according to claim 2, wherein said second measuring means are adapted to provide a fourth signal, the third and the fourth signal being responsive to the diameters of the part of the second workpiece on two cross-sections corresponding to said distinct sections of the part of the first workpiece, the processing and control means receiving said fourth signal. 
     
     
       4. The apparatus according to claim 3, wherein said machine tool is a grinding machine and said processing and control means comprise processing circuits for comparing said first signal with said third signal, for providing an enabling signal upon the obtainment of a pre-set matching play, the processing circuits being moreover adapted to calculate a signal responsive to the difference between actual values of play between the parts of the workpieces in correspondence with said cross-sections, the processing circuits being further adapted to control, upon the obtainment of said enabling signal, a regulation of the grinding machine for compensating, during the proceeding of the machining, the difference between said actual values of play, and to control the machining stop depending on a comparison of the first and third signal, for obtaining the desired matching play. 
     
     
       5. The apparatus according to claim 4, wherein said processing circuits are adapted to control, upon the obtainment of said enabling signal and before the controlling of said regulation, the starting of a spark-out phase. 
     
     
       6. The apparatus according to claim 4 or claim 5, wherein the first workpiece is a shaft and said part already machined defines a bore, said first measuring means comprising two measuring heads adapted to check the relevant diameters at the ends of the shaft and said second measuring means comprising two measuring heads adapted to check the relevant diameters of the bore. 
     
     
       7. The apparatus according to claim 2, wherein said machine tool is a grinding machine and said processing and control means comprise processing circuits adapted to compare the difference between said first signal and said third signal with a reference value, for controlling subsequently the regulation of the grinding machine for correcting the deviations from cylindricity of the part of the first workpiece depending on the comparison of the first and second signal, the processing circuits being moreover adapted to control the machining stop upon the obtainment of the desired matching play depending on a comparison of the first and third signal. 
     
     
       8. The apparatus according to claim 4 or claim 7, wherein said processing and control means comprise an open-loop circuit for controlling said regulation of the grinding machine. 
     
     
       9. The apparatus according to claim 4, wherein said first and second measuring means comprise indicating devices for indicating the values of the play between the parts of the two workpieces in correspondence with said cross-sections and for indicating the difference between said play values. 
     
     
       10. The apparatus according to claim 7, wherein said first and second measuring means comprise indicating devices for indicating the value of play between the parts of the first and the second workpiece and the deviation from cylindricity of the part of the first workpiece. 
     
     
       11. The apparatus according to claim 2, wherein said first and second measuring means are adapted to measure the maximum and minimum deviations, from the nominal values, of the diameters of said cross-sections of the part of the first workpiece and of at least a cross-section of the part of the second workpiece, the processing and control means being adapted to process said deviations for controlling and regulating the machine tool.